IAs prison populations across the countrygrow, there is a need for greater understanding of the health needs of this diverse population. Prisoninmates often come from poverty situations where health care options are limited. They are likely to have used both legal and illegal substances,and they engage in activities that put them at risk of injury both from accidents and violent interactions.These factors combine to place this populationat high risk of experiencing Traumatic Brain Injury (TBI) which may be medically under treated and exacerbated by subsequent substance use. TBI often results in behavioral symptoms which, if untreated, can lead to difficulties in adjustment to prison life and may make successful reintegration into the communityupon release less likely as well. Currently there is little research available on the prevalence of a historyof TBI among prison inmates. This study will begin to address this gap in our understanding by developing and validating a brief interview instrument to assess history of TBI among prison inmates. This research builds upon an ongoing study of the prevalence of mental health problems among inmates in the Federal Bureau of Prisons (BOP). This study (The Mental Health Prevalence Study: MHPS) has collected both self report and archival data from over 2000 inmatesfrom 13 prison units across the country. The TBI instrument willbe administered to a sample of 200 inmateswho participated in that study. Selecting respondents from this original pool will permit us to access psychological and behavioral data that would not otherwise be possible to collect in a study of this size. In addition to the data from the MHPS, we will also administer a battery of neuropsychological tests which measure behavioral, functional, and cognitive deficits commonly accompanying TBI. The TBI instrument will be assessed for reliability and validated for use in this population using factor analytic and correlational methods. In addition to assessing the psychometric properties of this instrument, the research team, in collaboration with the CDC, will develop a proposal to conduct a full scale TBI prevalence survey in the BOP to assess actual prevalence and incidence of TBI in what is currently the largest prison system in the United States.